1. Field of the Invention
This invention relates to a method for altering the width of the focal zone generated by an integral lens system.
2. Description of the Prior Art
An integral lens system acts to concentrate energy at a predetermined location known to those skilled in the art as the focal zone. The concentration of such energy in a compact focal zone is useful both in the optical and ultrasonic art. It is especially useful in the field of ultrasonic inspection of power generating equipment, such as turbines and generators.
In the prior art, it is at times advantageous to alter the focal zone, and especially the lateral dimension thereof, in order to provide a more widely dispersed laterally extending concentration of sonic energy. Prior art methods for altering the focal zone produced by lens systems require intricate remachining of the lensing surfaces of the integral lens member so that the refinished lens system produces a focal zone different from the previous focal zone in terms of lateral dispersion. However, such refinishing and remachining is an extremely difficult and complex process. Also, the cost of machinery sufficient to adequately provide the refinishing process, especially in the area when refinished surfaces on adjacent portions of the lens surface must be melded together so as not to create an optical or sonic discontinuity in the lensing surface. As a result, such refinishing and remachining processes are necessarily costly.